1. Field of the Invention
The present invention relates to an object recognition apparatus and method performing recognition of objects on and around a road, on which a vehicle is traveling, on the basis of images picked up by an on-vehicle camera, and to a camera attitude parameter generating apparatus and method producing camera attitude parameters which represent the attitude of the on-vehicle camera with respect to the road, and are used for the recognition of objects.
2. Description of Related Art
Various techniques have been proposed to pick up images ahead of or behind a vehicle by an on-vehicle camera, and to recognize objects in the images. For example, if the foregoing vehicles are recognized by processing the foregoing images of the vehicle, which are acquired by the on-vehicle camera, the results can be used in an automatic operation of the vehicle, thereby preventing an accident. Specifically, if other vehicles abnormally approach the vehicle, an accident can be prevented by automatic steering or brakes. Furthermore, if road signs can be recognized, the information associated with the road signs can be used in a navigation apparatus for directing a course of the vehicle.
When recognizing an object in an image acquired by an on-vehicle camera, the position of the object in the image changes every moment. A high efficiency recognition of such object which moves in an image from moment to moment requires accurate camera attitude parameters which represent the attitude of the on-vehicle camera with respect to the road, that is, to a quiescent coordinate system. In other words, the behavior of an object in an image can be estimated on the basis of the accurate camera attitude parameters. Using the estimation results makes it possible to cut off an image portion, which would include the object, from the image acquired, and to carry out an image recognition processing of the cut off image portion, which will improve the image processing efficiency. Here, the camera attitude parameters include the yaw angle, the roll angle and the pitch angle of the on-vehicle camera with respect to a road (a quiescent coordinate system) and a traverse deviation distance of the on-vehicle camera from a reference line parallel to the road.
The camera attitude parameters may be changed by variables inherent to the vehicle such as acceleration, speed, bearing of the vehicle. Many of these variables can be provided by a position detection processing unit and an anti-lock brake unit, which are mounted on the vehicle. The position detection processing unit has a basic function of detecting the current position of the vehicle on the basis of the mileage and bearing of the vehicle, and displaying them on a display unit with a road map. The anti-lock brake unit has a g-sensor detecting the acceleration (including deceleration) of the vehicle, and a wheel speed sensor detecting the rotational speed of a wheel, and controls the brake pressure on the basis of the detection results, thereby preventing the wheels from locking, and achieving an optimum braking.
In a conventional system, however, these data handled by the position detection processing unit or the anti-lock brake unit are not utilized to obtain the camera attitude parameters, and hence, the accuracy and efficiency of obtaining the camera attitude parameters are insufficient.
Since various objects such as vehicles, pedestrians, road signs will appear or disappear in a scene picked up by the on-vehicle camera, an object that comes into a scene of the on-vehicle camera at a particular processing period must be identified in the scene at the next processing period. To achieve this, a tracking recognition of an object must be implemented by taking account of the position of the object, the change in the position, a positional detection error, identification of a still or moving state, patterns of the object, or the like. The tracking recognition of an object requires a quick processing because it is carried out by successively acquiring images by the on-vehicle camera while the vehicle is traveling.